The present invention relates to a method for separating and removing selectively boron trifluoride from a fluid containing boron trifluoride or its complex and a method for recovering the boron trifluoride.
Furthermore, the present invention relates to a method for producing polyolefin using a boron trifluoride complex catalyst, as polymerization catalyst, comprising boron trifluoride and a complexing agent. More particularly, the invention relates to a method in which a polymerization product containing polybutene or olefin oligomer obtained by olefin polymerization is brought into contact with metal fluoride to remove boron trifluoride recovering the complexing agent from the complex catalyst. Furthermore, it relates to a method comprising the steps of heating the produced metal tetrafluoroborate so as to separate metal fluoride and boron trifluoride gas, and reproducing boron trifluoride complex catalyst for reuse from the recovered boron trifluoride and the complexing agent.
Boron trifluoride and boron trifluoride complex composed of boron trifluoride and a complexing agent (also called as xe2x80x9cligandxe2x80x9d) are used widely in industrial fields as catalysts in various chemical reactions such as alkylation, isomerization, polymerization, decomposition and dehydration. These catalysts are used in the form of boron trifluoride alone or in the form of coordination compound containing any of various complexing agents in an appropriate proportion relative to boron trifluoride in accordance with an intended reaction.
After the termination of reaction using boron trifluoride catalyst or its complex catalyst, it is necessary to deactivate the boron trifluoride.
For this purpose, the catalyst is usually neutralized in an aqueous solution of basic substance such as ammonia, caustic soda or lime, then it is washed with water. However, the catalyst treated in such a method cannot be used again. Furthermore, waste liquid containing the used alkali and fluoride as the neutralization product of boron trifluoride, is discarded from the processes of neutralization and washing. In recent years, therefore, it has been demanded to take measures to deal with the problem in environmental pollution. Still further, because boron trifluoride is expensive in itself, its recovering and reusing are advantageous in the viewpoints of economy and environmental protection. Therefore, various kinds of recovering methods have hitherto been proposed.
In the following, a process for producing polybutene and olefin oligomer using boron trifluoride complex will be described.
Polymers having double bond structure of vinylidene groups are especially useful in that they can react with maleic acid or the like at high rate. Therefore, some processes are proposed for introducing much more vinylidene structures into polybutene.
For example, in U.S. Pat. No. 4,152,499, it is disclosed that isobutene is polymerized using, as polymerization catalyst, gaseous boron trifluoride or a boron trifluoride complex catalyst with complexing agent of water or alcohol. In this case, isobutene is polymerized in the temperature range of xe2x88x9250xc2x0 C. to +30xc2x0 C., and polyisobutene having a polymerization degree of 10 to 100 is obtained. It is described in this reference that vinylidene double bonds can be introduced into 60 to 90% of terminal positions.
Furthermore, in European Patent No. 0 145 235 A, it is disclosed that polymerization was carried out using a complex catalyst previously prepared from boron trifluoride and C1 to C8 alcohols, and vinylidene double bond could be introduced into 70 to 90% of terminal positions of polyisobutene.
As described above, boron trifluoride complex catalysts are often used for producing polybutene such as polyisobutene. For each complex catalyst, specific complexing agent is selected, and its molar coordination number is also specified.
Concerning olefin oligomers, processes for producing olefin oligomer by polymerizing olefins having 6 to 18 carbon atoms are widely known. The olefin oligomer is useful as raw material for lubricating oil such as car engine oil, aircraft hydraulic oil and electrically insulating oil. In recent years especially, olefin oligomers having comparatively low viscosity are considered to be quite useful as a raw material for car engine oil. More particularly, oligomers of linear xcex1-olefin having 10 carbon atoms, i.e., 1-decene, especially oligomers mainly containing trimer of 1-decene have attracted considerable attention.
As the foregoing method for producing oligomers, cationic polymerization processes using a catalyst of Lewis acid such as boron trifluoride is practiced widely. Meanwhile, several attempts have been done widely in order to develop the methods of controlled polymerization and those which are inexpensive and free from environmental pollution.
For example, in Japanese Laid-Open Patent Publication No. H06-287211, it is disclosed that olefin oligomers of comparatively low viscosity can be produced by a method using boron trifluoride catalyst. In this case, however, there is a problem that the controlling of reaction rate of polymerization is difficult. As the countermeasure to this, polymerization method for obtaining olefin oligomers is disclosed, which method uses as polymerization catalyst a boron trifluoride complex catalyst that has boron trifluoride incorporated in a complex.
In the production of olefin oligomers in recent years, boron trifluoride complex catalysts are usually preferred. For each complex catalyst, as in the case of production of polyisobutene, specific complexing agent is selected, and its molar coordination number is also specified.
After the termination of polymerization reaction for polybutene or olefin oligomer as above, boron trifluoride in complex must be removed from the reaction mixture. For this purpose, the reaction mixture is usually neutralized with an aqueous solution of basic substance such as ammonia, caustic soda and lime, then it is washed with water. However, as mentioned above, an environmental problem and other disadvantages are pointed out.
In the following, prior art on the removing and recovering of boron trifluoride used in various kinds of reactions will be described.
For example, methods for separating boron trifluoride complex catalysts from reaction mixtures by heating are proposed. In U.S. Pat. No. 4,263,467 by A. M. Madgavkar, et al., a method is disclosed wherein boron trifluoride is taken out as gas by causing a reaction mixture to move slowly on a floor made of inert metal or ceramics.
In Japanese Laid-Open Patent Publication No. H06-287211, a system using a boron trifluoride complex catalyst is described. It is disclosed that a reaction mixture is heated so as to generate boron trifluoride gas, excess complexing agent is brought into contact with the generated gas to form a new complex, and the complex is recycled to a reactor for reuse.
Further, in Japanese Laid-Open Patent Publication No. H08-333472, the production of xcex1-olefin oligomer is described, wherein boron trifluoride complex catalyst composed of boron trifluoride and reaction accelerator of C1 to C8 alkanol is used. In this case, the method comprises a process of thermally decomposing the complex in product fluid to obtain boron trifluoride gas and contacting the gas with a low temperature stream of a-olefin oligomer containing an accelerator, for reuse.
However, in these methods, highly reactive boron trifluoride or its complex is heated in the coexistence of reaction mixture, so that the composition of the reaction mixture may be influenced seriously. In the case of the olefin oligomer containing particularly much xcex1-olefin structure as mentioned above, isomerization or thermal deterioration of olefin is caused by heating it in the coexistence of the complex. As a result, the quality of product deteriorates.
As the other device for recovering boron trifluoride complex catalysts described in U.S. Pat. Nos. 4,454,366 and 4,384,162 by R. F. Vogel, et al., it is disclosed that polyvinyl alcohol is used in order to take out boron trifluoride in oligomerization. In U.S. Pat. No. 4,433,197 by R. F. Vogel, et al., the reaction product is brought into contact with silica to remove boron trifluoride. In U.S. Pat. No. 4,429,177 by N. E. Morganson, et al. and U.S. Pat. Nos. 4,213,001 and 4,308,414 by A. M. Madgavkar, et al., silica is also used as absorbent for boron trifluoride in oligomerization. In U.S. Pat. No. 4,394,296 by A. M. Madgavkar, et al., it is disclosed that boron trifluoride and cocatalyst of silica hydrate are used in an oligomerization process, then silica is filtered off for recycling.
As to these prior arts of removing boron trifluoride using polyvinyl alcohol or silica, the present inventors carried out confirmatory test. As a result, the following important information was obtained on the reuse of both the absorbents.
That is, in the former case using polyvinyl alcohol, the alcohol itself is poor in thermal resistance, so that it cannot stand repeated uses as absorbent after desorbing boron trifluoride by heating.
In the latter case using silica, functional groups such as siloxane and silanol group existent in a silica molecule decompose boron trifluoride when boron trifluoride is removed. Therefore, it is difficult to recover boron trifluoride in a reusable state.
As another method for removing boron trifluoride, it is disclosed in U.S. Pat. No. 4,981,578 by L. T. Tycer, et al. that boron trifluoride is removed by bringing a product stream of olefin oligomer into contact with a solid or aqueous solution of KF, NaF or NH4F. In U.S. Pat. No. 4,956,513 by H. W. Walker, et al., it is disclosed that boron trifluoride is removed from a product of oligomerization by extracting with water.
However, it is intended in the above methods only to remove boron trifluoride from a product stream containing boron trifluoride complex catalyst but they do not aim to recover boron trifluoride in reusable state. Furthermore, in the former method, even though boron trifluoride is removed using KF, NaF or NH4F, thermal decomposition temperatures of sodium tetrafluoroborate (NaBF4) and potassium tetrafluoroborate (KBF4) are higher than 650xc2x0 C. and 750xc2x0 C., respectively. Considering the energy cost required for thermal decomposition in recovering boron trifluoride, the method is not acceptable in industrial working. Furthermore, NH4F is very low in thermal resistance in itself and decomposes into NH3 and HF, so that its use is not practical.
Still further, in a method for recovering boron trifluoride described in U.S. Pat. No. 2,997,371, acrylonitrile is polymerized on active carbon and boron trifluoride in gas is removed by polyacrylonitrile supported on the active carbon. However, the capacity of adsorption is not sufficient. Further, the temperature for desorbing boron trifluoride is not lower than the melting point of polyacrylonitrile, so that polyacrylonitrile cannot be used repeatedly after desorption.
From the disclosures of various production processes using boron trifluoride complex catalysts in the above prior art, it is understood that various methods for removing boron trifluoride were proposed and various efforts were made during their developments. However, under the present situations, any economical method for recovering boron trifluoride in reusable form without causing environmental pollution, has not been proposed.
An object of the present invention is, therefore, to provide a method to remove at high efficiency the expensive and detrimental boron trifluoride from a fluid containing boron trifluoride or its complex by economical means without causing environmental pollution. Another object of the invention is to provide a method to recover boron trifluoride in a reusable form.
A further other object of the invention is to apply the forgoing recovery method to the production of polyolefin such as polybutene and olefin oligomer, and to provide a method for producing polyolefin, which method comprises recovering boron trifluoride and a complexing agent separately, preparing the complex again and reusing it as catalyst.
The present inventors investigated according to the foregoing objects, they have found out an epoch-making method, wherein boron trifluoride is removed from a fluid containing boron trifluoride or its complex and boron trifluoride is recovered in a reusable form. Furthermore, as application of the above method to the production of polyolefin, they have found out a method for producing polyolefin to accomplish the present invention, which method comprises removing and recovering boron trifluoride from a reaction mixture, preparing a complex and reusing it.
Thus, a first aspect of the present invention relates to a method for removing boron trifluoride, which method comprises the step of bringing a fluid containing boron trifluoride or boron trifluoride complex into contact with a metal fluoride shown in the following formula [1], thereby causing the metal fluoride to adsorb selectively boron trifluoride in the complex.
MFnxe2x80x83xe2x80x83[1]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
A second aspect of the present invention relates to a method for removing boron trifluoride as described in the first aspect, wherein the contact temperature is 100xc2x0 C. or below.
A third aspect of the present invention relates to a method for removing boron trifluoride as described in the first aspect, wherein the boron trifluoride complex is the one that is formed of boron trifluoride and an organic or inorganic polar compound.
A fourth aspect of the present invention relates to a method for removing boron trifluoride as described in the third aspect, wherein the organic or inorganic polar compound is the one selected from the group consisting of oxygen-containing compound, nitrogen-containing compound, sulfur-containing compound, phosphorus-containing compound and inorganic acid.
A fifth aspect of the present invention relates to a method for removing boron trifluoride as described in the fourth aspect, wherein the oxygen-containing compound is the one selected from the group consisting of water, alcohols, ethers, phenols, ketones, aldehydes, esters, organic acids and acid anhydrides.
A sixth aspect of the present invention relates to a method for recovering boron trifluoride comprising the following Steps:
(Step 1): to bring a fluid containing boron trifluoride or a boron trifluoride complex into contact with metal fluoride shown in the following formula [1], thereby causing the metal fluoride to adsorb selectively the boron trifluoride (BF3) in the complex to form a metal tetrafluoroborate shown in the following formula [2],
MFnxe2x80x83xe2x80x83[1]
M(BF4)nxe2x80x83xe2x80x83[2]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
(Step 2): to heat the metal tetrafluoroborate obtained in the Step 1 in the temperature range of 100 to 600xc2x0 C. to obtain boron trifluoride and the metal fluoride.
A seventh aspect of the present invention relates to a method for recovering boron trifluoride as described in the sixth aspect, wherein the temperature for heating the metal tetrafluoroborate in the Step 2 is 500xc2x0 C. or below.
An eighth aspect of the present invention relates to a method for producing polyolefin using olefin having 4 or more carbon atoms as a feed material, which method comprises the following steps (I) to (III):
Step (I): to polymerize olefin in a liquid phase in the presence of a boron trifluoride complex catalyst comprising boron trifluoride and complexing agent,
Step (II): to bring the reaction mixture having at least a part of dispersed and/or dissolved boron trifluoride complex into contact with metal fluoride shown in the following formula [1], thereby causing the metal fluoride to adsorb selectively boron trifluoride (BF3) in the complex catalyst to form metal tetra-fluoroborate shown in the following formula [2],
MFnxe2x80x83xe2x80x83[1]
M(BF4)nxe2x80x83xe2x80x83[2]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
Step (III): to recover the reaction mixture containing the complexing agent from which boron trifluoride was separated by adsorption.
A ninth aspect of the present invention relates to a method for producing polyolefin using olefin having 4 or more carbon atoms as a feed material, which method comprises the following Steps (I) to (V):
Step (I): to polymerize olefin in a liquid phase in the presence of boron trifluoride complex catalyst comprising boron trifluoride and a complexing agent,
Step (II): to bring the reaction mixture having at least a part of dispersed and/or dissolved boron trifluoride complex into contact with metal fluoride shown in the following formula [1], thereby causing the metal fluoride to adsorb selectively boron trifluoride (BF3) in the complex catalyst to form metal tetrafluoroborate shown in the following formula [2],
MFnxe2x80x83xe2x80x83[1]
M(BF4)nxe2x80x83xe2x80x83[2]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
Step (III): to recover the reaction mixture containing the complexing agent from which boron trifluoride was separated by adsorption,
Step (IV): to heat the metal tetrafluoroborate obtained in the Step (II) in the temperature range of 160 to 600xc2x0 C. to obtain boron trifluoride and the metal fluoride
Step (V): to polymerize olefins in a liquid phase using at least a part of the recovered boron trifluoride as catalyst.
A tenth aspect of the present invention relates to a method for producing polyolefin using olefin having 4 or more carbon atoms as a feed material, which method comprises the following Steps (I) to (VI):
Step (I): to polymerize olefin in a liquid phase in the presence of boron trifluoride complex catalyst comprising boron trifluoride and a complexing agent,
Step (II): to bring the reaction mixture having at least a part of dispersed and/or dissolved boron trifluoride complex into contact with metal fluoride shown in the following formula [1], thereby causing the metal fluoride to adsorb selectively boron trifluoride (BF3) in the complex catalyst to form metal tetrafluoroborate shown in the following formula [2],
MFnxe2x80x83xe2x80x83[1]
M(BF4)nxe2x80x83xe2x80x83[2]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
Step (III): to recover the reaction mixture containing the complexing agent from which boron trifluoride was separated by adsorption,
Step (IV): to heat the metal tetrafluoroborate obtained in the Step (II) in the temperature range of 160 to 600xc2x0 C. to obtain boron trifluoride and the metal fluoride,
Step (V): to recover the complexing agent which is liberated into the reaction mixture when boron trifluoride in the complex catalyst is adsorbed in the Step (II),
Step (VI): to prepare new boron trifluoride complex catalyst using at least a part of the boron trifluoride recovered from the Step (IV) and the complexing agent recovered from the Step (V) respectively, and to polymerize olefin in a liquid phase using the new catalyst.
An eleventh aspect of the present invention relates to a method for producing polyolefin as described in any of eighth to tenth aspects, wherein the feed material for polymerization is C4 olefin and the polyolefin is polybutene.
A twelfth aspect of the present invention relates to a method for producing polyolefin as describe in any of eighth to tenth aspects, wherein the feed material for polymerization is olefin having 5 or more carbon atoms (hereinafter referred to as xe2x80x9colefins of C5 or higherxe2x80x9d) and the polyolefin is olefin oligomer.
A thirteenth aspect of the present invention relates to a method for producing polyolefin as described in any of eighth to twelfth aspects, wherein the concentration of olefin in the feed material in the liquid phase polymerization is at least 5% by weight.
A fourteenth aspect of the present invention relates to a method for producing polyolefin as described in any of eighth to twelfth aspects, characterized in that the temperature of the reaction mixture in contact with the metal fluoride is in the range of xe2x88x92100 to +160xc2x0 C., preferably xe2x88x9230 to +50xc2x0 C.
A fifteenth aspect of the present invention relates to a method for producing polyolefin as described in any of eighth to twelfth aspects, characterized in that the molar ratio of boron trifluoride relative to the complexing agent in the boron trifluoride complex catalyst is in the range of 0.01:1 to 2:1.
A sixteenth aspect of the present invention relates to a method for producing polyolefin as described in any of eighth to twelfth aspects, characterized in that the molecular weight of the polyolefin is in the range of 100 to 100,000.
In the following, the present invention will be described in more detail.
Boron trifluoride and boron trifluoride complex comprising boron trifluoride and complexing agent are classified in Friedel-Crafts type catalyst such as AlCl3, FeCl3, and sulfuric acid in view of catalytic effect. Furthermore, it is known that the catalytic performance is superior to AlCl3, FeCl3, sulfuric acid and so forth in that it has the effect to suppress side reaction other than main reaction. Therefore, boron trifluoride and its various complexes are widely used in industrial fields as catalysts for various chemical reactions such as alkylation, isomerization, polymerization, decomposition and dehydration.
For example, when ethylbenzene is produced by gas phase alkylation using ethylene obtained by naphtha cracking and benzene, boron trifluoride is utilized.
For producing alkylbenzene that has a large market in use for synthetic detergent, antioxidant and so forth, liquid phase alkylation is carried out using lower olefin and aromatic compounds. In this production, boron trifluoride or its complex is similarly used.
C9 aromatic olefin fraction and C5 diolefin fraction obtained by naphtha cracking can be polymerized separately or in a mixture with acid catalyst to obtain hydrocarbon resin having low molecular weight. The obtained resin is usually called as petroleum resin and it is used widely in the fields of adhesives, printing inks and so forth. As a polymerization catalyst for producing this resin, boron trifluoride or its complex is also used widely in industrial field.
As described above, boron trifluoride or its complex are used for various purposes as catalysts in the field of chemical industry. In addition, they are also used widely in other fields such as medicines and semiconductors.
In the above reactions such as alkylation, the fluid of reaction mixture containing boron trifluoride or its complex flows out from a reaction system after the reaction. A typical example of the fluid containing boron trifluoride or its complex used in the present invention is, as described above, the fluid from a producing process using boron trifluoride or its complex as catalyst. Generally, the fluid is a liquid or gas that does not form any complex with boron trifluoride. It can be a gas such as air and nitrogen gas, or a liquid of organic compound such as hydrocarbon, alcohol, ether, ketone and ester, or their vapors, as long as they do not form any complex. In such a fluid, boron trifluoride, its complex, or both of them in certain cases exist in the state of solution or dispersion.
However, when a fluid that dissolves metal fluorides or metal tetra-fluoroborate (reaction products of metal fluoride and boron trifluoride) is used in the step for adsorbing and removing boron trifluoride, it is not preferable that the above adsorption step is hardly accomplished. Exemplified as the unsuitable fluids in the present invention are fluid of ammonium salt, hydrofluoric acid or hydrochloric acid, and fluid containing any of these compounds.
As the subject matter to be treated according to the present invention, a fluid containing boron trifluoride complexes as well as a fluid containing boron trifluoride itself can be used. Even when the fluid contains the complex, it is possible to adsorb only boron trifluoride by treating it with the method of the present invention.
Therefore, as the modes of fluid that can be used in the present invention, there are exemplified by organic liquid mixtures containing boron trifluoride or its complex in dispersed or dissolved state in an organic liquid; organic liquid mixtures containing the vapor of boron trifluoride or its complex in dissolved or dispersed state in an organic liquid; and gaseous mixtures containing the vapor of boron trifluoride or its complex in a certain gas such as waste gas.
Furthermore, only in the case of using barium fluoride as the above metal fluoride, boron trifluoride forms complexes, by coordinate bond, with oxygen-containing compounds such as alcohol, ether, ketone and ester. Therefore, when these oxygen-containing compounds are contained in a fluid, the amount of barium fluoride used for adsorbing and removing boron trifluoride according to the present invention increases. Accordingly, it is preferable that the fluid containing boron trifluoride or its complex does not contain oxygen-containing compounds, because the amount of barium fluoride to be used can be decreased. In the case of metal fluorides other than barium fluoride, the above problem need not be considered in particular.
Exemplified as complexing agents for forming boron trifluoride complex catalysts suitable for the present invention are specific polar compounds. They are, for example, organic or inorganic polar compounds such as oxygen-containing compounds like alcohols, ethers, phenols, ketones, aldehydes, esters, organic acids and acid anhydrides, nitrogen-containing compounds, sulfur-containing compounds, phosphorus-containing compounds and inorganic acids.
As alcohols specifically, aromatic or C1 to C20 aliphatic alcohols can be used, wherein the C1 to C20 carbon structure can be either linear alkyl group or branched alkyl group, that is, the alkyl group may be n-, sec- or tert-alkyl group, alicyclic group, or alkyl group containing alicyclic ring. More specifically, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, benzyl alcohol, cyclohexanol and the like can be used, though the alcohols are not limited to these compounds. Further, polyhydric alcohols such as diols and triols can be used.
As for ethers, those containing aromatic or C1 to C20 aliphatic hydrocarbon group can be used. The C1 to C20 carbon structure can be either a linear alkyl group or a branched alkyl group, that is, the alkyl group can be n-, sec- or tert-alkyl group, alicyclic group, or alkyl group containing alicyclic ring. Specifically, dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, methyl propyl ether, ethyl propyl ether, dibutyl ether, methyl butyl ether, ethyl butyl ether, propyl butyl ether, dipentyl ether, or phenyl methyl ether, phenyl ethyl ether, diphenyl ether, cyclohexyl methyl ether, cyclohexyl ethyl ether and the like can be used.
As for phenols, monohydric to trihydric phenols are suitable, and specifically, phenol, cresol and the like are preferable.
As for ketones, those containing aromatic or C1 to C6 hydrocarbon groups can be used. The C1 to C6 carbon structure can be either a linear alkyl group or a branched alkyl group, that is, the alkyl group can be n-, sec- or tert-alkyl group, alicyclic group, or alkyl group containing alicyclic ring. Specifically, methyl ethyl ketone, diethyl ketone, methyl butyl ketone, cyclohexanone and the like can be used.
As for esters, those containing ester combinations formed with a component of aromatic or C1 to C6 aliphatic alcohol and a component of aromatic or C1 to C6 aliphatic carboxylic acid or phosphoric acid can be used. The C1 to C6 carbon structure can be either a linear alkyl group or a branched alkyl group, that is, the alkyl group can be n-, sec- or tert-alkyl group, alicyclic group, or alkyl group containing alicyclic ring. Specifically, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, ethyl hexanoate, ethyl benzoate, and complete esters of phosphoric acid such as tributyl phosphate can be used.
As for organic acids, aromatic or C1 to C6 aliphatic carboxylic acids, halogen-substituted products of these acids, phosphoric acid and partial esters comprising phosphoric acid and aromatic or C1 to C6 aliphatic alcohols can be used. The C1 to C6 carbon structure can be either a linear alkyl group or a branched alkyl group, that is, the alkyl group can be n-, sec- or tert-alkyl group, alicyclic group, or alkyl group containing alicyclic ring. Specifically, formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, benzoic acid, diethyl phosphate and so forth can be used.
These complexing agents can be used singly in each complex system, and can be also used in a mixture containing two or more kinds in an appropriate ratio. These complexes can be prepared according to the well-known methods. For example, the complex can be prepared previously. Besides, after putting boron trifluoride and one or more complexing agents into a reaction system in a certain ratio separately or simultaneously, they can be formed into boron trifluoride complex in a reaction liquid.
In a complex used in the present invention, the molar ratio of boron trifluoride to a complexing agent is not particularly limited. Any complex can be used regardless of the molar ratio. However, it is usually in the range of 0.01 to 100, inclusive.
When the boron trifluoride contained in a fluid is a complex as mentioned above, the concentration of boron trifluoride may be sometimes rather high. However, it is usually preferable to use a dilute solution of boron trifluoride in order to increase the efficiency of removing. Specifically, the concentration of boron trifluoride is 10% by weight or less, and preferably less than 5% by weight. The lower the concentration is, the higher the efficiency of removing is. Therefore, the lower limit of the concentration is not determined particularly. The dilution can be done appropriately so that the concentration may be in the above range. As fluids for dilution, any kind of diluent can be used as long as it does not form a complex with boron trifluoride. For example, it can be selected from the liquids exemplified above.
In the following, the metal fluorides used for adsorbing boron trifluoride in the present invention will be explained one after another, namely, lithium fluoride, calcium fluoride, strontium fluoride and barium fluoride.
In the first place, lithium fluoride is used largely in various industries including fluorescent substance, optical glass, ceramic filter, flux for welding, glaze and so forth. In the present invention, any kind of substance may be used such as natural substances, synthetic substances, and those obtained from industrial wastes. As a natural substance, it is preferable to select the material that is refined up to 98% or more in lithium fluoride content.
Furthermore, it is known that lithium fluoride can be synthesized from lithium hydroxide or lithium carbonate and hydrofluoric acid according to the reaction shown in the following formula [3] or [4]. The synthetic substance produced by this method can also be used. The lithium fluoride synthesized by these reactions is separated by operations such as gravity settling or filtration. Then, it can be used intact, however, it is more favorable that the lithium fluoride is washed with water or alkali, taking the advantage of small solubility of lithium fluoride in water, then heated and dried for use in the method of the present invention.
HF+LiOHxe2x86x92LiF+H2Oxe2x80x83xe2x80x83[3]
2HF+Li2CO3xe2x86x922LiF+H2O+CO2xe2x80x83xe2x80x83[4]
Furthermore, in the production process using hydrogen fluoride or else, hydrogen fluoride is sometimes neutralized according to the above formula [3] or [4] to deactivate catalyst. In this case, the by-product of lithium fluoride is formed as an industrial waste. This lithium fluoride as the by-product can also be used.
Next, calcium fluoride is used largely in various industries including iron and steel works, nickel refinery, and other industries such as glass, enamel and cement. In the present invention, any kind of materials obtained from natural substances, synthetic substances and industrial wastes can be used.
As for the natural substance, the well known xe2x80x9cfluoritexe2x80x9d can be used. It is an ordinary natural ore produced largely in many countries in the world including Mexico, Russia, France, Spain, China, Thailand, United States of America, Italy, South Africa and so forth. It is desirable to select the colorless, highly pure ore containing calcium fluoride of 98% or more.
Furthermore, it is known that calcium fluoride can be synthesized from hydrofluoric acid (HF) and slaked lime (Ca(OH)2) or calcium chloride (CaCl2) according to the reaction shown in the following formula [5] or [6], and the synthetic substance produced by this method can be also used. The calcium fluoride synthesized by these reactions is separated by operations such as gravity settling or filtration. Then, it can be used intact, however, it is more preferable that the calcium fluoride is washed with water or alkali, taking advantage of small solubility of calcium fluoride in water, then it is heated, dried and used in the present invention.
xe2x80x832HF+Ca(OH)2xe2x86x92CaF2+2H2Oxe2x80x83xe2x80x83[5]
2HF+CaCl2xe2x86x92CaF2+2HClxe2x80x83xe2x80x83[6]
Furthermore, in producing alkylbenzene or the like, hydrogen fluoride or else is sometimes used. After the end of reaction, hydrogen fluoride is usually neutralized according to the reaction shown in the above formula [5] or [6] to deactivate catalysts. In this case, the by-product of calcium fluoride is produced as industrial waste. This calcium fluoride as by-product can also be used.
Next, strontium fluoride is used largely in various industries including fluorescent substance, optical glass, ceramics filter and so forth. In the present invention, any kind of materials may be used among natural substance, synthetic substance, substance made from industrial wastes and so forth.
As a natural substance, it is preferable to select the one that is refined so highly that strontium fluoride is contained in 98% or more.
Further, it is known that strontium fluoride can be synthesized from strontium carbonate and hydrofluoric acid according to the reaction shown in the following formula [7], and the synthetic substance obtained by this method can be also used. The strontium fluoride synthesized by these reactions is separated by operations such as gravity settling or filtration. Then, it can be used intact, however, it is more favorable that the strontium fluoride is washed with water or alkali, taking the advantage of little solubility of strontium fluoride in water, then it is heated, dried and used in the present invention.
2HF+SrCO3xe2x86x92SrF2+H2O+CO2xe2x80x83xe2x80x83[7]
Furthermore, in production processes using a catalyst of hydrogen fluoride, hydrogen fluoride is neutralized in certain cases according to the above formula [7] to deactivate the catalyst. In this case, a by-product of strontium fluoride is produced as industrial waste. This strontium fluoride as by-product can be also used.
Next, barium fluoride is used largely in various industries including flux for enamel wares, matting agent, carbon brush for electric motor, thermal treatment of metal, preservative treatment, refining of highly pure aluminum, luminescent carbon for projection, flux for welding, glaze and so forth. In the present invention, any kind may be used among natural substance, synthetic substance, substance made from industrial wastes and so forth.
As a natural substance, it is preferable to select the one that is refined so highly that barium fluoride is contained in 98% or more.
Furthermore, it is known that barium fluoride can be synthesized from barium carbonate and hydrofluoric acid according to the reaction shown in the following formula [8], and the synthetic substance by this method can be also used. The barium fluoride synthesized by these reactions is separated by operations such as gravity settling or filtration. Then, it can be used intact, however, it is more preferable that the barium fluoride is washed with water or alkali, taking advantage of little solubility of barium fluoride in water, then heated, dried and used in the present invention.
2HF+BaCO3xe2x86x92BaF2+H2O+CO2xe2x80x83xe2x80x83[8]
Furthermore, in production processes using hydrogen fluoride, it is neutralized in certain cases according to the above formula [8] to deactivate catalysts. In this case, a by-product of barium fluoride is produced as industrial waste. This barium fluoride as by-product can be also used.
When a fluid containing boron trifluoride or its complex is brought into contact with the above metal fluoride (MFn), the reaction shown in the following formula [9] or [10] progresses easily, so that the metal fluoride is transformed into a metal tetrafluoroborate (M(BF4)n). Still further, at that time, the complexing agent in catalyst is released into the reaction mixture in liberated form. As a result, only the intended boron trifluoride can be caught and removed from the reaction mixture.
nBF3+MFnxe2x86x92M(BF4)nxe2x80x83xe2x80x83[9]
n[BF3xe2x88x92(complexing agent)]+MFnxe2x86x92M(BF4)n+n(complexing agent)xe2x80x83xe2x80x83[10]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
As to the temperature at which boron trifluoride is adsorbed and removed, each metal fluoride has its own acceptable maximum temperature because the efficiency of chemical adsorption varies depending on the kind of metal fluoride. That is, the following temperatures can be adopted: 160xc2x0 C. or below for lithium fluoride, 200xc2x0 C. or below for calcium fluoride and 250xc2x0 C. or below for strontium fluoride and barium fluoride. However, considering the changes of composition and chemical structure of the product, the desirable range of adsorption temperature is 100xc2x0 C. or below. The phase of fluid for contacting operation can be any of gas, liquid and mixed phase containing both of them.
All the above metal fluorides (MFn) have colorless crystal structures of cubic system. Among them, calcium fluoride, strontium fluoride and barium fluoride have xe2x80x9cfluorite structurexe2x80x9d. The metal tetrafluoroborate (M(BF4)n) which is formed after adsorbing boron trifluoride is known to have a colorless crystal structure of rhombic system, according to the report, for example, by T. H. Jordan, et al. (Acta Crystallogr., Sect. B, B31 [3] (1975), p. 669-672). Accordingly, both metal fluoride and metal tetrafluoroborate are very stable inorganic crystalline substances. Changes of the crystal structure before and after adsorption can be observed easily by X-ray diffraction analysis.
The method for bringing a fluid into contact with a metal fluoride is not limited in particular. For example, a fixed bed packed with metal fluoride alone or with an inert inorganic filler containing metal fluoride or the like can allow the passage of the fluid containing boron trifluoride or its complex. As inert inorganic fillers, active carbon, packing made of stainless steel and so forth are used, but the materials are not limited to the above, and the shape of them is not limited either.
It is not necessary to calcine the metal fluoride completely. However, when the recovered boron trifluoride is reused with avoiding moisture, it is preferable to use the metal fluorides after calcining until the moisture is released.
The particle diameter of metal fluoride to be used is not limited in particular. For example, the commercially available metal fluoride is in the form of fine particles in the range of 1 to 10 xcexcm in particle size distribution. These powder particles can be used after forming it into uniform particles having suitable size distribution. In order to increase the efficiency for adsorbing boron trifluoride, it is preferable to increase the surface area of metal fluoride as adsorbent. From this point of view, it is preferable that the particle size is as small as possible. However, in order to facilitate the adsorbing operation, the particle diameter may be selected appropriately.
Furthermore, the shape of metal fluoride is not especially limited either. For example, the cross section of each particle can be ordinarily circular, or particles may be hollow or a special form such as porous. It is preferable to select the particle shape appropriately in view of the purpose.
The contacting operation for adsorption can be carried out in any of flow type using an adsorption pipe or column packed with particles of metal fluoride and so forth as mentioned above, or in batch type. The contact time is not limited particularly and can be determined appropriately. In flow type operation, space velocity can be usually selected in the range of 0.01 to 10 hrxe2x88x921.
When a metal fluoride is lithium fluoride, the molar amount of metal fluoride required for removing boron trifluoride completely in a batch type must be the same as or more than the molar amount of boron trifluoride contained in a fluid treated. When a metal fluoride is calcium fluoride, strontium fluoride or barium fluoride, the molar amount of metal fluoride must be not less than 0.5 times as large as the molar amount of boron trifluoride. In order to increase the efficiency of removing, it is preferable to increase further the amount of metal fluoride, which amount can be selected appropriately.
By the above-mentioned method of contacting a fluid containing boron trifluoride or its complex with metal fluoride, the boron trifluoride in the above fluid is adsorbed chemically by metal fluoride, and then separated and removed from the fluid.
After adsorption, metal fluoride with adsorbed boron trifluoride can be separated from the system by an appropriate method.
The operation of desorption described in the following can be carried out in the adsorption tube or column. Otherwise, it can also be carried out after the metal fluoride is transferred into another apparatus.
In order to desorb the boron trifluoride from metal fluoride and recover boron trifluoride in a reusable state, metal tetrafluoroborate (M(BF4)n) formed by adsorption is heated. It is possible to convert the metal tetrafluoroborate into pure boron trifluoride gas and the original adsorbent of metal fluoride according to the reaction shown in the following formula [11].
M(BF4)nxe2x86x92nBF3+MFnxe2x80x83xe2x80x83[11]
wherein M is a metal atom such as lithium, calcium, strontium or barium and n is 1 or 2.
The heating can be carried out under the existence of suitable inert gas such as nitrogen. Heating can also be carried out in a suitable organic solvent, as long as the solvent is inert. The temperature for desorption of boron trifluoride gas is 100xc2x0 C. or above. In order to increase the rate of desorption sufficiently, it is desirable to carry out at temperatures of 160xc2x0 C. or above. However, as shown in the following, the temperature required for the sufficient desorption of boron trifluoride varies depending on the kind of metal fluoride selected. Therefore, it is desirable to select the temperature for desorption appropriately.
The upper limit of the temperature required for desorption is not limited in particular, because all of metal fluorides used in the present invention are stable crystals, which do not melt up to about 1,000xc2x0 C. That is, each of lithium fluoride up to about 850xc2x0 C., calcium fluoride and strontium fluoride up to 1,400xc2x0 C., and barium fluoride up to about 1,350xc2x0 C. is a stable crystal that does not melt in inert gases.
However, an extremely high temperature of above 600xc2x0 C. is unnecessary essentially, that is, high temperature causes unfavorably increase of energy cost, decomposition of organic solvent, and corrosion of apparatus by boron trifluoride gas. Furthermore, it is known that an oxide is formed when strontium fluoride is heated at a temperature above 1,000xc2x0 C. in the air.
The time required for desorption of boron trifluoride is not especially limited if the temperature is in the above described ranges. The longer the time of heating is, the higher the rate of desorption of boron trifluoride is. However, the longer time is not economical, so that the time is usually set to 100 hours or less.
When a metal fluoride as adsorbent is used repeatedly, it is preferable economically to keep the rate of desorption on an appropriate level.
By the above operation of heating, boron trifluoride is recovered in the form of highly pure boron trifluoride without suffering decomposition. The adsorbent is restored to the original metal fluoride of high purity. Therefore, the metal fluoride used for adsorption and desorption in the present invention can be used repeatedly as occasion demands.
Because the desorbed boron trifluoride is highly pure, it is recovered by suitable means and used for appropriate process. For example, it can be reused for the process, from which the treated fluid was obtained. Furthermore, the desorbed boron trifluoride can be absorbed or adsorbed by solid alkali or the like to be discarded.
In the following, a method for recovering complex catalyst and reusing it for reaction will be explained, wherein the above process for removing and recovering boron trifluoride is applied to the production of polyolefin using boron trifluoride complex catalyst.
Both production processes of polybutene and olefin oligomer are carried out by cationic polymerization of olefin, and boron trifluoride complex catalyst is used preferably as polymerization catalyst. After these reactions, at least a part of boron trifluoride complex catalyst exists stably in dissolved and/or dispersed state in reaction mixture. It is difficult to separate the complex catalyst from the reaction mixture as it stands and to reuse them. Accordingly, by adopting the above method for recovering in the present invention, the production method can be improved markedly.
In the production of polybutene, C4 olefins such as butadiene, isobutene, butene-1 and cis- or trans-butene-2 are mainly polymerized using boron trifluoride complex catalyst. C4 olefins can also be used for polymerization as a mixture together with C2 to C20 aliphatic olefins such as ethylene, propylene, isoprene, pentene and hexene-1; C8 to C10 aromatic olefins such as styrene and vinyl toluene; and alicyclic olefins such as DCPD.
As industrial feed materials, it is possible to use C5 fraction containing aliphatic olefins such as piperylene, or C4 fraction containing olefins such as 1-butene and trans- or cis-2-butene as well as isobutene, further, isobutane and n-butane.
Next, in the production of olefin oligomer, the C5 or higher olefins used as feed materials for polymerization are not limited particularly. Any olefin can be used as long as cationic polymerization can be carried out using boron trifluoride complex catalyst. Among olefins of C5 or higher, those having 6 to 18 carbon atoms are desirable, and those having 8 to 14 carbon atoms are more desirable. Specifically, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene and so forth are used. These olefins can be used for polymerization singly or in a mixture.
As olefins of C5 or higher, any olefin can be used among the olefin having double bonds in the terminal position of carbon chain and the inner olefin having double bonds inside carbon chain. However, it is preferable to use xcex1-olefin, especially 1-decene having 10 carbon atoms.
In polymerization, the concentration of olefin present in a feed material is preferably in the range of 5 to 100% by weight. The concentration of olefin of lower than 5% by weight is unfavorable practically because its economical disadvantage is large.
Solvent for dilution is not needed particularly. However, solvents inert to the reaction can be used appropriately in addition to the olefins if desired. Exemplified as solvents are saturated chain hydrocarbons including n-paraffins such as n-butane and n-hexane, and isoparaffins such as isobutane and isooctane; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane and decalin; and halogenated hydrocarbons such as carbon tetrachloride, chloroform and methylene chloride.
The kinds of complexing agents forming complexes with boron trifluoride and the method for forming complexes are the same as mentioned above. The molar ratio of boron trifluoride and complexing agent is preferably in the range of 0.01:1 to 2:1. If the molar ratio of boron trifluoride to complexing agent is lower than 0.01, the activity of catalyst is too low for proceeding the intended polymerization. On the other hand, if the molar ratio of boron trifluoride against complexing agent is higher than 2, the amount of boron trifluoride is too much as compared with complexing agent so as to keep a stable coordination. As a result, the molar ratio of boron trifluoride against complexing agent cannot be maintained in catalyst recovery. When the recovered boron trifluoride complex catalyst is reused as described later, the above operation such as adjustment of molar ratio is necessary. Therefore, it is important to control so that the molar coordination ratio would not change.
In cationic polymerization of olefins, the use amount of boron trifluoride is usually 0.0001 to 0.5 mole to 1 mole of polymerizable olefin components. The use amount of boron trifluoride changes depending on the kind of olefin, the temperature in polymerization system and so forth. For example, when olefin is 1-decene and the temperature of polymerization is 25xc2x0 C. in the production of an olefin oligomer, the amount of boron trifluoride is about 0.20 g/100 g-olefin.
In the following, the conditions of liquid phase polymerization in the Step (I) will be explained.
In the first place, in the polymerization of C4 olefin, the temperature of polymerization is set in the range of xe2x88x92100xc2x0 C. to +50xc2x0 C., preferably xe2x88x9240xc2x0 C. to +10xc2x0 C. If the temperature is lower than this range, the conversion rate of C4 olefin is suppressed. On the other hand, if the temperature is higher than that range, the conversion rate is also suppressed, moreover, undesired side reactions such as isomerization and rearrangement are caused to occur.
As the type of reaction, any of continuous type and batch-wise type can be adopted. In view of industrial production, the continuous type is more economical and efficient. In the case of continuous type, the contact time of feed material with catalyst is important, and it is preferably in the range of 5 minutes to 4 hours. If the contact time is less than 5 minutes, sufficient conversion rate of C4 olefin cannot be attained. On the other hand, if it is more than 4 hours, economical loss is large. Furthermore, by contacting the olefin with catalysts for a long period of time, side reactions such as isomerization and rearrangement of the produced butylene polymer are accelerated. Therefore, both cases are not preferable.
In order to improve the commercial profit in the production of butylene polymer, it is desirable that the conversion rate of C4 fraction, for example, C4 olefins in C4 raffinate is higher. By adopting the conditions for polymerization in the present invention, it is possible to attain the conversion rate of isobutene of 80 to 100%.
On the other hand, in the production of olefin oligomer, the temperature of polymerization is usually xe2x88x9220xc2x0 C. to +90xc2x0 C., preferably 0 to 50xc2x0 C. The pressure of polymerization is in the range of 0 to 3.5 MPaxc2x7G, preferably 0.001 to 0.5 MPaxc2x7G. The resident time of polymerization is 10 minutes to 24 hours, preferably 1 to 16 hours. As to the type of polymerization, any of batch-wise type and continuous type can be adopted.
After the polymerization, a reaction liquid flows out, which contains unreacted components, produced butylene polymer or olefin oligomer and catalyst. In this reaction mixture, boron trifluoride complex catalyst is dissolved or dispersed.
Next, in the Step (II), boron trifluoride is adsorbed and removed from the reaction mixture containing at least a part of the above boron trifluoride complex catalyst that is dissolved and/or dispersed. The reaction mixture and metal fluorides are brought into contact together in the temperature range of xe2x88x92100xc2x0 C. to +160xc2x0 C., inclusive, to form metal tetrafluoroborate sown in the above formula [9] or [10]. In this temperature range, the efficiency of chemisorption by boron trifluoride is high. As long as the above mixture is brought into contact in gas phase and/or liquid phase, any temperature of 160xc2x0 C. or below can be adopted.
However, when boron trifluoride complex catalyst having high activity is heated in the existence of a reaction mixture, in the case of the production of polybutene, vinylidene structures in molecules are isomerized to cause the deterioration of product quality. In the case of producing olefin oligomer, product quality might be also deteriorated owing to the change of compositions and chemical structures. Accordingly, the temperature of adsorption is preferably in the range of +50xc2x0 C. or below, further preferably xe2x88x9230xc2x0 C. to +50xc2x0 C. in each case.
The preferable number average molecular weight of polybutene or olefin oligomer obtained in the present invention is in the range of 100 to 100,000. The effect of removing boron trifluoride in boron trifluoride complex catalyst depends largely on the viscosity of reaction liquid. When polybutene of a small degree of polymerization is produced, the viscosity of reaction liquid is smaller than that obtained when the product of a large degree of polymerization is obtained. Therefore, the efficiency of dispersion in the former case is higher. However, polybutene having a molecular weight less than 100 is not useful, because the molecular weight is too small as the product of polybutene. When the viscosity of a reaction liquid is extremely high, dispersion of metal fluoride and removing by adsorption of boron trifluoride are insufficient. From the viewpoint as above, it is preferable that the viscosity of the present reaction mixture is 10,000 cP (10 Paxc2x7s) or less at the temperature of contacting with metal fluoride.
Furthermore, by adding an inert solvent to the reaction mixture in order to adjust the viscosity of reaction system within the above-mentioned limit, the reaction mixture can be used for removing boron trifluoride of complex catalyst. However, if the molecular weight exceeds 100,000, the amount of solvent for dilution required for separating reaction liquid and adsorbent increases to excess beyond the economical limit.
Using the above method, boron trifluoride in boron trifluoride complex catalysts is subjected to chemisorption by contact with metal fluorides and it is separated from reaction mixture.
Boron trifluoride is removed by the above adsorption, then in the Step (III), the intended products of polyolefins such as polybutene and olefin oligomer can be obtained from the reaction mixture, for example, by a suitable separation method such as distillation. Furthermore, if necessary, complex catalyst contained in the produced polyolefins can be removed by a well-known method such as neutralization. The removal of complex catalyst in polyolefins can be carried out easily, because most of complex catalyst is already removed.
Further, in the Step (IV), the metal tetrafluoroborate obtained in the Step (II) is heated to temperatures in the range of 160 to 600xc2x0 C., and restored to the pure boron trifluoride and the original metal fluoride as adsorbent according to the reaction shown in the above formula [11].
Moreover, while boron trifluoride is separated and recovered by desorption, complexing agent in boron trifluoride complex catalyst can also be recovered completely from the reaction mixture. More precisely, when boron trifluoride is adsorbed and removed from boron trifluoride complex catalyst, the complex is decomposed and metal fluoride captures boron trifluoride, while the complexing agent is released into the reaction mixture.
The liberated complexing agent can be recovered by distillation or the like method in the Step (V). Therefore, for the purpose of further reducing the cost, it is possible to recover the liberated complexing agent from the reaction mixture and prepare a boron trifluoride complex catalyst again using the recovered complexing agent and the boron trifluoride recovered from the other step. Incidentally, the complexing agent need not be always completely recovered, and the required amount of fresh complexing agent may be supplemented appropriately.
Furthermore, when complex catalyst is recovered and reused as catalyst for producing polybutene or olefin oligomer, attention must be paid so that the coordination number of the complexing agent in a complex catalyst would not be changed. The complexing agent coordinated in a complex show the required catalytic function only after the coordination number is also specified. However, coordination number is liable to change depending on the environmental conditions such as temperature. With the change of coordination number, catalyst functions differ. Therefore, in the Step (VI), where the boron trifluoride and the complexing agent each recovered are utilized, the complex must be prepared again so that they can have the coordination number that can show the required catalytic functions.
By the above operations, it is possible to use the boron trifluoride complex catalyst specified in coordination number again in the step for polymerizing polybutene.